Photochemical Reactions Research Articles

The impacts of photochemical loss on the source apportionment of ambient volatile organic compounds: A case study in Northern China

Volatile organic compounds (VOCs) play a crucial role as precursors in the formation of ozone (O3) and secondary PM2.5. It is well-established that some VOC species exhibit high photochemical reactivity, leading to deviations between measured and initial concentrations. Therefore, precise source apportionment must consider these photochemical reaction which called photochemical losses. The study was conducted in Langfang, which located in an important site for pollution transferring to Beijing, with August to October as the sampling period. The initial concentrations of the VOC species were estimated using a photochemical age-based parameterization method. The effects of photochemical losses on source apportionment were compared by the positive matrix factorization (PMF) results, based on observed and initial concentration data. The results showed that neglecting photochemical losses would result in an underestimation of VOCs concentration by 6.7% compared to the measured values obtained in this study. Furthermore, olefins and aromatic hydrocarbons were found to be the key components involved in photochemical reactions, with a photochemical loss rate of 28.3% and 23.7%, respectively. VOCs source apportionment revealed that the impact of photochemical loss on source apportionment was significant. Results indicated that biogenic sources (−6.8%) and solvent usage (−5.9%) made a higher contribution based on initial VOCs compared to measured VOCs, while gasoline vehicular emissions showed a lower contribution (+7.9%) than that observed from measured VOCs data. Analysis results also demonstrated that the combustion sources accounted for 14.2% based on measured concentrations and that accounted for 9.5% based on initial concentrations.

Visible-light-induced four-component difunctionalization of alkenes to construct phosphorodithioate-containing quinoxalin-2(1H)-ones

A facile visible-light-induced 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) catalyzed four-component reaction of alkenes, quinoxalin-2(1H)-ones, P4S10 and alcohols has been developed at room temperature. This tandem reaction provides an efficient strategy for the construction of various phosphorodithioate-containing quinoxalin-2(1H)-ones with moderate to good yields by using air (dioxygen) as the green oxidant. Experimental studies revealed a radical process was involved in this photochemical reaction.

Source apportionment and formation of warm season ozone pollution in Chengdu based on CMAQ-ISAM

In this study, the WRF-CMAQ model integrated with BEM urban canopy model was used to simulate the concentrations of Ozone (O3) and its precursors, NOx and VOCs, in warm season of Chengdu, conduct source apportionment and formation analysis. The results show that the O3 in Chengdu exhibits a west-high/east-low spatial pattern, attributable to nearly 40% contribution from boundary sources representing the transport role of the Sichuan Basin, regional sources from districts emitting high precursor concentrations, and increasing biogenic contributions from western areas due to rising BVOCs emissions during the warm season. NOx from traffic and VOCs from industrial sources, both prevalent in Chengdu's high urban density areas, chemically react to form O3, making these sectors primary contributors to O3. NOx photochemical reactions producing O3 occur at 150 m–2500 m with peak generation rates of 10 μg/(m3·hr). Ground-level NO titration removal is most significant during heavy traffic (14:00–21:00), ranging from −70 to −200 μg/(m3·hr). O3 is replenished through similar rates of daytime vertical diffusion and nighttime horizontal advection, correlating with urban density across regions. Controlling Chengdu's warm season O3 requires focusing on long-distance external transport and regional precursor emission reductions, with strategies tailored to local urban characteristics.

Photo‐Induced Difluoromethylation‐Cyclization of Indoles Using Tetrazole Sulfone Reagent Under Visible Light

AbstractPolycyclic indoles are prevailed in natural products, pharmaceuticals and biologically active compounds. Herein is described photo‐induced difluoromethylation‐cyclization of N‐alkene tethered indoles to synthesis of tetrahydropyrido[1,2‐a]indole using 5‐((difluoromethyl)sulfonyl)‐1‐phenyl‐1H‐tetrazole as a CF2H radical source. This photochemical reaction tolerates an array of functional groups like ester, cyano, ketone, halide, ether, aldehyde and heteocycles. Mechanistic experiments indicated that the difluoromethyl radical and the single electron transfer were involved.

Prediction of photodynamics of 200nm excited cyclobutanone with linear response electronic structure and abinitio multiple spawning.

Simulations of photochemical reaction dynamics have been a challenge to the theoretical chemistry community for some time. In an effort to determine the predictive character of current approaches, we predict the results of an upcoming ultrafast diffraction experiment on the photodynamics of cyclobutanone after excitation to the lowest lying Rydberg state (S2). A picosecond of nonadiabatic dynamics is described with abinitio multiple spawning. We use both time dependent density functional theory (TDDFT) and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) theory for the underlying electronic structure theory. We find that the lifetime of the S2 state is more than a picosecond (with both TDDFT and EOM-CCSD). The predicted ultrafast electron diffraction spectrum exhibits numerous structural features, but weak time dependence over the course of the simulations.

Implications of ozone transport on air quality in the Sichuan Basin, China.

Ozone pollution is formed through complex chemical and physical processes closely associated with emissions, photochemical reactions, and meteorological conditions. The objective of this study is to quantify the contributions of meteorological chemical formation, vertical transport, and horizontal transport to air quality during spring and summer in different regions of the Sichuan Basin. The Community Multi-scale Air Quality (CMAQ) with the Integrated Process Rate (IPR) was employed to simulate the months of April and July 2021 in the Sichuan Basin. The results indicate that both the spring and summer chemical formation of ozone in the urban centre show negative values, while the surrounding urban areas contribute positively, with chemical formation ranging from 0 to 10 μg·m-3. The maximum ozone level due to horizontal transport in the urban centre exceeds 20 μg·m-3, whereas horizontal transport in the surrounding urban areas exhibits negative values, with transport contributions concentrated within the range of -5 to 0 μg·m-3. The vertical transport in the central and southern parts of the basin shows positive values, with transport contributions ranging from 0 to 10 μg·m-3, and the urban centre exhibits relatively stronger vertical transport with contributions ranging from 10 to 20 μg·m-3. Although the chemical formation contribution in the urban centre is relatively small due to high nitrogen oxide emissions, vertical and horizontal transport play significant roles and are among the key factors contributing to ozone pollution formation.

First Structured Uranium‐Based Monoliths Produced via Vat Photopolymerization for Nuclear Applications

AbstractUranium plays an unquestionable role in the framework of nuclear physics, biology, and radiopharmacy. Moreover, uranyl ion UO22+ offers an immense variety of applications due to the unique photosensitivity of its complexes. The excited state of uranyl cation is indeed accessible under ultraviolet‐visible (UV–vis) light, readily producing radical species UO22+* upon light irradiation. Herein, an innovative synthesis protocol is presented to explore the use of uranyl cations as photocatalyst systems for photocurable sol–gel‐based formulations, coupling the photochemical reactions of uranyl cations with photopolymerization‐based additive manufacturing processes. Additive manufacturing has nowadays revolutionized the production of complex structures with arbitrary geometries and has opened up enticing opportunities for innovative technological breakthroughs and highly tailorable systems. The fabrication of micro‐architected components is shown via vat photopolymerization, namely, the Digital Light Processing technique, and ‐3D) printed parts are converted into uranium dicarbide (UC2)/carbon nanocomposite upon carbothermal reduction. This uranyl‐mediated additive manufacturing process constitutes the first application of the synergistic role of uranyl motifs in a photopolymer platform, demonstrating for the first time the possibility to directly pattern uranium‐based materials in complex structures.

Diarylethene derivative photoionization control via two-color two-laser optical manipulation in the presence of cyclodextrins

In this study, the photodynamics of 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene (DE) was investigated in the presence of α-, β- and γ-cyclodextrin (CD) inclusion complexes and under the influence of one- and two-laser excitations. Thus, this study aimed to elucidate the ionization quantum yield of DE and how it is affected by the type of CD and laser configuration. Specifically, DE/CD was flash photolyzed using a single laser (355 nm) or a double laser (355 nm and 532 nm) and observed at a wavelength of 720 nm to examine the transient absorption of hydrated electrons. The ionization efficiency with the two lasers was found to exceed that with the single laser. This suggests the existence of a two-step process involving S0→S1 and S1→Sn singlet transitions in the two-photon ionization (TPI) of DE. Furthermore, when the ring-closing isomer of DE was initiated via laser irradiation at 532 nm, the photoionization efficiency increased, especially in the presence of γ-CD. This implies that the 532-nm irradiation, which is not directly involved in TPI, contributed to promoting the TPI of DE, thus increasing its photo-steady state (saturation). Thus, the possibility of using CD-containing lasers to control photochemical reactions with photo-steady state processes was demonstrated. This investigation contributes to a broader understanding of the potential applications and underlying mechanisms of photochromic materials influenced by multi-laser interactions.

Photochemical modification of a diamond surface using a pulsed UV laser as the energy source

The use of an excimer benchtop pulsed UV laser as the energy source for the photochemical modification of the surface of diamond films is reported. Boron-doped nanocrystalline diamond (NCD) films were deposited on Si wafers via plasma-enhanced chemical vapour deposition (PECVD). The as-deposited films were characterised by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Following characterisation, the surfaces of the films were subjected to a photochemical reaction with 2,2,2-trifluoroethyl undec-10-enoate using two different sources of radiation: a benchtop UV lamp (254 nm) and a KrF excimer pulsed UV laser (248 nm). The photochemically treated films were characterised by contact angle measurements and X-ray photoelectric spectroscopy (XPS) using non-treated films as a control. The use of a pulsed UV laser source was shown to reduce the photochemical reaction time from several hours to a few minutes.

Photoswitchable eutectogels with ultra-strength, high stretchability and adhesion for information encryption and multifunctional flexible sensor of signal transmission and human–computer interaction

Eutectogels are emerging as attractive soft conductors for flexible wearable electronics and next-generation human–computer interaction devices owing to their inherent environmental stability and high ionic conductivity. However, it remains a challenge to achieve efficient multifunctional integration of flexible wearable sensors through a convenient and environment-friendly approach. Herein, the eutectogel with excellent mechanical properties, self-healing, environmental tolerance, reversibly fluorescent and high conductivity was prepared via a facile UV-initiated one-step polymerization. Abundant hydrogen bonds and multiple dynamic interactions impart the eutectogel with excellent tensile strength (1.99 MPa), high stretchability (>1500 %), high toughness (20.85 MJ/m3), strong self-adhesion (192 kPa), and autonomously self-healing (>92 %) capabilities. Due to the dynamic photochemical reaction of the anthracene groups, the eutectogel exhibits tunable and reversible fluorescence. The eutectogel-based flexible wearable devices and wireless interaction systems can be used for non-contact information writing and transmission, motion monitoring, wireless communication, and human–computer interaction, which achieves the working modes of digital and visual signals complementing each other as well as efficient multifunctional integration. Therefore, this simple and environment-friendly design concept can provide new ideas for the development of multifunctional integrated portable flexible sensing devices and wireless interactive systems.

Ultrafast x-ray scattering and electronic coherence at avoided crossings: complete isotropic signals

Nonadiabatic transitions at conical intersections and avoided crossings play a pivotal role in shaping the outcomes of photochemical reactions. Using the photodissociation of LiF as a model, this theoretical study explores the application of gas phase nonresonant ultrafast x-ray scattering to map nonadiabatic transitions at an avoided crossing, utilizing the part of the scattering signal that probes electronic coherence directly. The presented scattering signals are rotationally averaged and calculated from two- rather than one-electron (transition) densities, which inherently accounts for all possible electronic transitions driven by the x-ray photon. This approach provides quantitative predictions of the experimental signals, thereby facilitating future experimental endeavors to observe nonadiabatic effects and coherent electron dynamics with ultrafast x-ray scattering.

Seasonal and height dynamics of volatile organic compounds in rubber plantation: Impacts on ozone and secondary organic aerosol formation

Rubber trees emit a range of volatile organic compounds (VOCs), including isoprene, monoterpenes, and sesquiterpenes, as part of their natural metabolism. These VOCs can significantly influence air quality through photochemical reactions that produce ozone and secondary organic aerosols (SOAs). This study examines the impact of VOCs detected in a rubber tree plantation in Northeastern Thailand on air quality, highlighting their role in atmospheric reactions that lead to the formation of ozone and SOAs. VOCs were collected at varying heights and seasons using Tenax-TA tubes paired with an atmospheric sampler pump and identified by gas chromatography–mass spectrometry. In total, 100 VOCs were identified, including alkanes, alkenes, terpenes, aromatics, and oxygenated VOCs. Principal Coordinate Analysis (PCoA) revealed distinct seasonal VOC profiles, with hydrocarbons, peaking in summer and terpenes in the rainy season. The Linear Mixed-Effects (LME) model indicates that VOC concentrations are more influenced by seasonal changes than by sampling heights. Secondary organic aerosol potential (SOAP) and ozone formation potential (OFP) of selected VOC species were also determined. The total SOAP ranged from 67.24 μg/m3 in summer to 17.87 μg/m3 in winter, while the total OFP ranged from 377.87 μg/m3 in summer to 139.39 μg/m3 in winter. Additionally, positive matrix factorization (PMF) analysis identified four main VOC sources: gasoline combustion (18.3 %), microbial activity (38.6 %), monoterpene emissions during latex production (15.0 %), and industrial sources (28.1 %). These findings provide essential information for managing air pollution in rubber tree plantations. By adopting focused air quality management strategies, plantation operators can mitigate the adverse effects of VOCs, promoting a healthier and more sustainable future.

Photoisomerization pathway of the microbial rhodopsin chromophore in solution

Photoisomerization is a key photochemical reaction in microbial and animal rhodopsins. It is well established that such photoisomerization is highly selective; all-trans to 13-cis, and 11-cis to all-trans forms in microbial and animal rhodopsins, respectively. Nevertheless, unusual photoisomerization pathways have been discovered recently in microbial rhodopsins. In an enzymerhodopsin NeoR, the all-trans chromophore is isomerized into the 7-cis form exclusively, which is stable at room temperature. Although, the 7-cis form is produced by illumination of retinal, formation of the 7-cis form was never reported for a protonated Schiff base of all-trans retinal in solution. Present HPLC analysis of retinal oximes prepared by hydroxylamine reaction revealed that all-trans and 7-cis forms cannot be separated from the syn peaks under the standard HPLC conditions, while it is possible by the analysis of the anti-peaks. Consequently, we found formation of the 7-cis form by the photoreaction of all-trans chromophore in solution, regardless of the protonation state of the Schiff base. Upon light absorption of all-trans protonated retinal Schiff base in solution, excited-state relaxation accompanies double-bond isomerization, producing 7-cis, 9-cis, 11-cis, or 13-cis form. In contrast, specific chromophore-protein interaction enforces selective isomerization into the 13-cis form in many microbial rhodopsins, but into 7-cis in NeoR.Graphical

Interaction between acid-tolerant alga Graesiella sp. MA1 and schwertmannite under long-term acidic condition

Schwertmannite (Sch), a typical Fe(III)-oxyhydroxysulphate mineral, is the precipitation reservoir of toxic elements in acid mine drainage (AMD). Acid-tolerant microbes in AMD can participate in the microbe-mediated transformation of Sch, while Sch affects the physiological characteristics of these acid-tolerant microbes. Based on our discovery of algae and Sch enrichment in a contaminated acid mine pit lake, we predicted the interaction between algae and Sch when incubated together. The acid-tolerant alga Graesiella sp. MA1 was isolated from the pit-lake surface water of an acidic mine and incubated with different contents of Sch. Sch was detected as the main product at the end of 81 d; however, there was a weak transformation. The presence of dissolved Fe(II) could be largely attributed to the photoreduction dissolution of Sch, which was promoted by Graesiella sp. MA1. The adaptation and growth phases of Graesiella sp. MA1 differed under Sch stress. The photosynthetic and metabolic activities increased and decreased at the adaptation and growth phases, respectively. The MDA contents and antioxidant activity of SOD, APX, and GSH in algal cells gradually enhanced as the Sch treatment content increased, indicating a defense strategy of Graesiella sp. MA1. Metabolomic analysis revealed that Sch affected the expression of significant differential metabolites in Graesiella sp. MA1. Organic carboxylic acid substances were essentially up-regulated in response to Sch stress. They were abundant in the medium-Sch system with the highest Fe(III) reduction, capable of complexing Fe(III), and underwent photochemical reactions via photo-induced charge transfer. The significant up-regulation of reducing sugars revealed the high energy requirement of Graesiella sp. MA1 under Sch stress. And first enriched KEGG pathway demonstrated the importance of sugar metabolism in Graesiella sp. MA1. Data acquired in this study provide novel insights into extreme acid stress adaptation of acid-tolerant algae and Sch, contributing to furthering understanding of AMD environments.

First Proof of Concept of a Click Inverse Electron Demand Diels-Alder Reaction for Assigning the Regiochemistry of Carbon-Carbon Double Bonds in Untargeted Lipidomics.

Lipidomics by high-resolution mass spectrometry (HRMS) has become a prominent tool in clinical chemistry due to the proven connections between lipid dysregulation and the insurgence of pathologies. However, it is difficult to achieve structural characterization beyond the fatty acid level by HRMS, especially when it comes to the regiochemistry of carbon-carbon double bonds, which play a major role in determining the properties of cell membranes. Several approaches have been proposed for elucidating the regiochemistry of double bonds, such as derivatization before MS analysis by photochemical reactions, which have shown great potential for their versatility but have the unavoidable drawback of splitting the MS signal. Among other possible approaches for derivatizing electron-rich double bonds, the emerging inverse-electron-demand Diels-Alder (IEDDA) reaction with tetrazines stands out for its unmatchable kinetics and has found several applications in basic biology and protein imaging. In this study, a catalyst-free click IEDDA reaction was employed for the first time to pinpoint carbon-carbon double bonds in free and conjugated fatty acids. Fatty acid and glycerophospholipid regioisomers were analyzed alone and in combination, demonstrating that the IEDDA reaction had click character and allowed the obtention of diagnostic product ions following MS/MS fragmentation as well as the possibility of performing relative quantitation of lipid regioisomers. The IEDDA protocol was later employed in an untargeted lipidomics study on plasma samples of patients suffering from prostate cancer and benign prostatic conditions, confirming the applicability of the proposed reaction to complex matrices of clinical interest.

Photochemical Stability and Reactivity of Sodium Pyruvate: Implications for Organic Analysis on Ceres

Photochemical Stability and Reactivity of Sodium Pyruvate: Implications for Organic Analysis on Ceres

Photoinitiated Single-Crystal to Single-Crystal Redox Transformations of Titanium-Oxo Clusters.

Titanium-oxo clusters can undergo photochemical reactions under UV light, resulting in the reduction of the titanium-oxo core and oxidation of surface ligands. This is an important step in photocatalytic processes in light-absorbing Ti/O-based clusters, metal-organic frameworks, and (nano)material surfaces; however, studying the direct outcome of this photochemical process is challenging due to the fragility of the immediate photoproducts. In this report, titanium-oxo clusters [TiO(OiPr)(L)]n (n = 4, L = O2PPh2, or n = 6, L = O2CCH2tBu) undergo a two-electron photoredox reaction in the single-crystal state via an irreversible single-crystal to single-crystal (SC-SC) transformation initiated by a UV laser. The process is monitored by single crystal X-ray diffraction revealing the photoreduction of the cluster with coproduction of an (oxidized) acetone ligand, which is retained in the structure as a ligand to Ti(3+). The results demonstrate that photochemistry of inorganic molecules can be studied in the single crystal phase, allowing characterization of photoproducts which are unstable in the solution phase.

Photoenhanced sulfate formation by the heterogeneous uptake of SO2 on non-photoactive mineral dust

Abstract. Heterogeneous uptake of SO2 on mineral dust is a predominant formation pathway of sulfates, whereas the contribution of photo-induced SO2 oxidation to sulfates on the dust interfaces still remains unclear. Here, we investigated heterogeneous photochemical reactions of SO2 on five mineral oxides (SiO2, kaolinite, Al2O3, MgO, and CaO) without photocatalytic activity. Light enhanced the uptake of SO2, and its enhancement effects negatively depended on the basicity of mineral oxides. The initial uptake coefficient (γ0,BET) and the steady-state uptake coefficient (γs,BET) of SO2 positively relied on light intensity, relative humidity (RH), and O2 content, while they exhibited a negative relationship with the initial SO2 concentration. Rapid sulfate formation during photo-induced heterogeneous reactions of SO2 with all mineral oxides was confirmed to be ubiquitous, and H2O and O2 played key roles in the conversion of SO2 to sulfates. In particular, triplet states of SO2 (3SO2) were suggested to be the trigger for photochemical sulfate formation. Atmospheric implications supported a potential contribution of interfacial SO2 photochemistry on non-photoactive mineral dust to atmospheric sulfate sources.

Sustainable Synthesis through Catalyst-Free Photoinduced Cascaded Bond Formation.

The beginning of photochemical reactions revolutionized synthetic chemistry through sustainable practices. This review explores cutting-edge developments in leveraging light-induced processes for generating cascaded C-C and C-hetero bonds without catalysts. Significantly, catalyst-free photoinduced methodologies have garnered considerable attention, especially in the creation of varied heterocyclic frameworks for drug design and the synthesis of natural products. The article delves into underlying mechanisms, addresses limitations, and evaluates various methodologies, emphasizing the potential of photocatalyst and transition metal-free photochemical reactions to enhance sustainability. Divided into two sections, it covers recent strides in C-C and C-heteroatom and multiple C-heteroatom bond formation reactions.

A New Approach for On-Chip Production of Biological Microgels Using Photochemical Cross-Linking.

Photochemical cross-linking is a key step for manufacturing microgels in numerous applications, including drug delivery, tissue engineering, material production, and wound healing. Existing photochemical cross-linking techniques in microfluidic devices rely on UV curing, which can cause cell and DNA damage. We address this challenge by developing a microfluidic workflow for producing microgels using visible light-driven photochemical cross-linking of aqueous droplets dispersed in a continuous oil phase. We report a proof-of-concept to construct microgels from the protein Bovine Serum Albumin (BSA) with [Ru(bpy)3]2+ mediated cross-linking. By controlling the capillary number of the continuous and dispersed phases, the volumetric flow rate, and the photochemical reaction time within the microfluidic tubing, we demonstrate the construction of protein microgels with controllable and uniform dimensions. Our technique can, in principle, be applied to a wide range of different proteins with biological and responsive properties. This work therefore bridges the gap between hydrogel manufacturing using visible light and microfluidic microgel templating, facilitating numerous biomedical applications.